7/14/1875 - A correspondent writes to the Sun as follows: I have received by mail from some unknown source a pamphlet entitled The Keely Motor. The first paragraph of this pamphlet is a quotation from a paper published by me some two years ago, in a New York scientific journal. I know nothing of the Keely Motor nor any of the persons connected with it. But for the benefit of the public I will say that I have in practical operation, capable of doing useful work, a simple apparatus which generates a constant pressure of fifteen pounds per square inch, without heat, chemical or electrical action, or the employment of any other materials than a small quantity of air and water. I use this low pressure only for convenience, but can at pleasure increase it indefinitely in the same apparatus. I can assure the public that producing a pressure only limited by the strength of a generator, from no other source of power than a small quantity of cold water and air moving slowly therein, is no "humbug," nor new discovery, but is a fact, long known to scientists and mathematicians. And, furthermore, the apparatus I have for effecting it cannot be patented by other parties. Respectfully yours, A. ARNOLD. Tenafly, N.J., July 4, 1875.